The present invention relates to vehicles that utilize implements and more specifically to a mechanism for releasably suspending an implement beneath such a vehicle.
Vehicles such as utility or lawn tractors are frequently operated with a variety of attachments and/or implements. Often one implement is used for a period of time and then removed to allow the tractor to be used with a different implement. Even if the implement is not frequently replaced with another, it must occasionally be removed and reinstalled as repairs, adjustments and/or maintenance is performed. Accordingly, it is desirable to have a mechanism for mounting implements so that they can be quickly and easily installed and/or removed.
Implements such as mower decks must be attached so they can be used at a variety of operating heights. Generally, mower decks are used to cut grass at heights varying between one and three and a half inches. To support the deck in a level configuration at each of the heights throughout its cutting range, the decks are mounted to swing on a parallelogram arrangement.
One suspension mechanism that mounts the mower deck between the front and rear wheels of the vehicle with an appropriate parallelogram arrangement and also facilitates quick and easy installation and removal is found in U.S. Pat. No. 5,025,617 (hereinafter referred to as xe2x80x9cthe ""617 patentxe2x80x9d), which is assigned to assignee of the present invention. That patent is incorporated by reference herein.
The mechanism described in the ""617 patent utilizes a pair of laterally spaced apart lift links pivotally connected to the tractor and to the rear of the implement deck. At the front of the deck, a generally rectangularly shaped hanger has its rear link or cross member pivotally received in hooks carried at the forward end of the deck and its front link or cross member pivotally received in hooks carried on the tractor. The sides of the hanger serve as draft links to support the forward end of the deck. The rear lift links and forward draft links of the hanger serve as the two opposite and equal length sides of a parallelogram support arrangement to assure even and level movement of the deck as it is adjusted throughout its vertical cut range. As shown in the ""617 patent, the pivotal connections at the upper and lower ends of the two rear lift links and at the upper and lower ends of the draft links provide the four corners of the parallelogram lift arrangement.
As the desire for improved grass cut quality has increased, the blade overlap on mower decks has increased. To provide this overlap, the fore and aft dimension of mower decks have increased. If the type of parallelogram suspension mechanism taught in the ""617 patent is to be used with larger decks and existing parallelogram lift linkages, then either the front or rear connections to the larger decks must be relocated. Since mower decks are mounted between the front and rear wheels of the vehicle, there is not enough tire clearance to shift larger decks rearwardly and pivotally connect the lift links to the rear of the deck. To shift the pivoting connection on the front of the deck forwardly beneath the tractor could relocate the lower forward corner of the parallelogram and adversely affect the lift geometry that provides for the deck to be raised or lowered evenly as the cut height is adjusted. Alternatively, changing the lift geometry on the vehicle would adversely affect all other mower decks that could be mounted on that vehicle, therefore eliminating commonality of attachment.
Accordingly, it would be desirable to provide an implement suspension mechanism of the type described in the ""617 patent that can be used with larger decks.
It would also be desirable to provide an implement suspension mechanism that can accommodate the larger mower decks without altering the parallelogram lift geometry presently available on many tractors.
Further, it would be desirable to provide a suspension mechanism that permits the connection between the front of larger decks and lower rear end of the front draft links to be located forwardly of the deck yet retain in its original location the pivotal connection with the deck that serves as one of the four parallelogram corners.
It would also be desirable to provide a suspension mechanism that maintains the parallelogram lift geometry to assure that the cut height of the deck is level from the front of the deck to its rear as it is adjusted through its range as well as a mechanism that allows the deck to be quickly and easily installed or removed.
Toward these ends, there is provided a pair of pivoting hooks on the front of the mower deck. The pivotal connection of the hooks with the deck serves as the front lower corner of the parallelogram lift arrangement. Since the location of this corner of the parallelogram is maintained, the lift geometry is maintained. The hooks are able to swing in an arc forwardly and downwardly to allow the rear crossbar of the hanger to be inserted into the throat of each pivoting hook. Since the hooks pivot forwardly and downwardly, the rear crossbar of the hanger can easily be inserted into or removed from them even though the front end of larger decks extends further forwardly. A stop is provided to prevent the hooks from swinging too far downwardly. As tension is provided to the draft links by a bell crank arrangement, the cross bar slides forwardly into the throat of the hooks and is retained in a line directly between the front lower pivot and front upper pivot of the parallelogram. In this way, the parallelogram lift geometry is maintained with larger decks throughout the range of vertical adjustment as cutting height is changed.
As is also taught in the ""617 patent, the bell crank arrangement is provided on the front crossbar of the hanger to tension or release the draft links. As the links are tensioned, the pivoting hooks on the mower deck swing upwardly with the draft links being retained in the proper parallelogram configuration.
With this arrangement, the proper mower deck lift geometry is realized with larger decks and the resulting cut height of the deck remains level throughout its range of adjustment.